Is taking half of a 60 mg Adderall pill the same as taking a 30 mg one?

Basically if I have 2 pills 1 that's 60 mg and one that's 30 mg would taking half of the 60 be the same and effect someone the same as taking the 30 dosage? At first it seems logical that it works that way but I wonder if the 30 mg is that dosage over the period of time it's meant for & half of the 60 mg would be stronger but for a short duration. I am no expert at all so please I welcome your input!